Field of the Invention
This invention relates to an apparatus for detecting abnormal hydraulic pressure of an automatic transmission, more specifically to an apparatus for appropriately detecting abnormally high pressure of hydraulic oil for controlling an automatic transmission.
Description of Related Art
A technique for detecting whether hydraulic pressure for controlling an automatic transmission has become abnormal is taught, for example, by Patent Reference 1 (Japanese Laid-Open Patent Application No. 2013-7402). The teaching of Patent Reference 1 is to use the slippage of rotational speed of a lock-up clutch as the basis for detecting whether a source pressure for controlling an automatic transmission is abnormally low.
The source pressure of an automatic transmission is the hydraulic pressure constituting the source of the control pressures for controlling the clutch and other mechanisms of the automatic transmission and, as such, must from the beginning be set to a higher pressure than the other control pressures. In view of this, the teaching of Patent Reference 1 is directed to appropriately detecting abnormal line pressure, particularly abnormally low line pressure.